Method for restoring original appearance of impregnated leather by dissolving the impregnant on the surface of the leather



NIETHOD FOR RESTORING ORIGINAL APPEAR- ANCE OF IMPREGNATED LEATHER BY DIS- SOLVING THE IMPREGNANT ON THE SUR- FACE OF THE LEATHER John H. Davis, Williamsport, Pa., assignor to the United States of America as represented by the Secretary of Commerce No Drawing. Application March 31, 1954, Serial No. 420,213

5 Claims. (Cl. 117-11) The present invention relates to a method for improving the appearance of leather and in particular to a method for restoring the appearance of impregnated leather to that of the untreated product.

Impregnation of leather with various oils, waxes, resins and polymers is being undertaken today by the leather industry to meet demands for an improved product. Improvements attained by impregnation are increased wear, better resistance to Water and chemicals, greater flex life, and ability to withstand high temperature and pressure.

In many cases however, impregnation of leather results in objectionable color or appearance so that the products rosin but it is miscible with acetone and will therefore value from a sales standpoint is materially reduced. This condition is especially true in the case of sole leather, where the customer or shoe manufacturer requires that the appearance of the product be maintained in keeping with previously set standards.

A number of attempts have been made to clean the leather but they have been only moderately successful at best. Since the impregnant penetrates the leather and does not lie only along the outer surfaces, it would seem logical that the method of cleaning would be to remove the surface impregnant without disturbing that which penetrated beyond the surface.

The difliculties which have been encountered in the past in attempting to remove the surface impregnant seem attributable to the fact that if the surface is cleaned with a solvent which is allowed to dry on the leather, capillary action will cause the impregnant, which had originally penetrated beyond the surface, to rise to the surface during the drying period of the solvent. Therefore the only effect upon the leather is to reduce the depth of penetration of the impregnant and at the same time leave the surface appearance practically the same.

The present invention employs a method which restores the original appearance of vegetable tanned crust sole leather after it has been impregnated with varied types of impregnants. The leather can then be dry or wet rolled, and finally waxed or brushed, as desired.

It is an object of the present invention to provide a simple method of restoring the appearance of impregnated leather to the appearance of ordinary untreated leather.

It is another object of the present invention to provide a method for improving the appearance of impregnated leather, which method is simple and cheap.

It is another object of the present invention to provide a rapid method for improving the appearance of impregnated leather.

Other uses and advantages of the invention will become apparent upon reference to the specification.

The present invention is based on the principle that one or more successive, rapid solvents for the particular impregnation material employed must first be used on the air-dry impregnated leather to effect removal of the impregnant from the leather surfaces. Then the leather must immediately be placed in one or more successive, poor solvents for the impregnant to effect the surface ice dilution and removal of the solvent, or solvents, originallyemployed and to stop solvent action on the impregnant.

It is necessary that each successive solvent be miscible with the preceding solvent. In other words, the leather is treated with a good solvent which dissolves the impregnant in the surface portion of the leather. Then the leather is treated with a second solvent before the first solvent has had time to dry. This second solvent is miscible with the first solvent but must be a poor solvent for the impregnant. Therefore the action on the impregnant is almost immediately stopped and the original solvent, which has dissolved therein the impregnant that was on the surface of the leather, is washed away, thereby preventing the capillary action which Was responsible for the failure of the prior cleaning processes. The principle of the invention is illustrated in the following typical examples.

Example 1 An example of the operation of the present invention is in the case Where leather has been treated with a polymerized wood rosin or perhaps an oil impregnant.

The rosin-impregnated leather is Washed in acetone which is a good solvent for such a rosin. This dissolves the rosin on the surface of the leather and the leather is then immediately washed in water. Water will not affect the dilute and wash away the resulting eluate. The action of the acetone is stopped immediately, and there is no opportunity for the above-mentioned capillary action to occur. The length of time the leather is washed with acetone 1 determines the amount of impregnant which will be v as gasoline to remove the surface rubber.

cleaned from the surface. In most cases from 30 to seconds have been found to be sufiicient. The washing with water is usually complete within 5 minutes.

Example 2 An example of treatments with successive solvents is when leather is treated with an impregnant'which is made up of both polymerized wood rosin and butyl rubber. In this case the leather is initially treated with an eluant such This action is stopped by Washing with acetone which is not a solvent for rubber but in which the gasoline is miscible. The acetone cleans the rosin from the surface and the action on the rosin is stopped by washing with water in which the acetone is miscible, but which will not dissolve the rosin. In this instance then, successive, rapid solvents are used, each solvent being miscible with the preceding solvent, but each successive solvent being a poor solvent for the succeeding impregnant materials which are being removed. The necessary immersions and washings are carried out in a manner and for time periods as described in Example 1.

Acetone may be replaced in the above examples by solvents of the ester, glycol, glycol ether, alcohol and ketone types while gasoline may be replaced by such materials as Varsol and other petroleum type solvents.

Where acetone is used it is necessary that the leather be washed almost immediately after cleaning the surface with acetone. However, the time intervals involved depend upon the volatility of the solvents, since if the original solvent is not highly volatile, the drying period will be greatly extended and the need for speed is correspondingly reduced.

This invention then provides a very simple method for solving What has been to date a very diflicult problem; that is, it provides impregnated leathers which have the surface appearance of natural or untreated leathers.

It will beapparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of my invention as defined in the appended claims.

What is claimed is:

1. A method for restoring the original appearance of leather which has been impregnated throughout the leather with an impregnant selected from the group consisting of rubber, oil, wax, and polymerized wood rosin, to increase wear, for better resistance to water and chemicals, greater flex life and ability to withstand high temperature and. pressure, comprising the steps of washing said impregnated leather in a solvent for the selected impregnant said solvent being selected from the group consisting of gasoline, Varsol, glycol ether, alcohol and ketones, for a time period suflicient to dissolve only the impregnant in the surface portions of said impregnated leather, removing the resulting eluate by washing said impregnated leather before said solvent dries with a second' organic solvent which is inert to said leather and which is miscible with said selected solvent and with water, and in which said impregnant is insoluble, and diluting and removing the eluate containing the second organic solvent by washing the impregnated leather in water.

2. A method for restoring the original appearance of leather which has been impregnated throughout the leather with at least two of the impregnants selected from the group consisting of rubber, oil, wax, and polymerized wood rosin, to increase wear, for better resistance to water and chemicals, greater flex life and ability to withstand high temperature and pressure, each of said impregnants being soluble in a different solvent, comprisingthe steps of successively washing said impregnated leather in the respective solvent for each of said impregnants, each successive solvent being applied before the previous solvent has dried, said solvent being selected from the group consisting of gasoline, Varsol, glycol ether, alcohol, and ketones, for a time period suflicient to dissolve only the impregnants in the surface portions of the impregnated leather, each of the solvents selected from said group of solvents employed during each of said successive washing steps being a solvent for only one of said impregnants, the solvent employed in each successive washing step being miscible withthe. solvent employed in the preceding washing step, the impregnant treated by the prior applied solvent being insoluble in each succeeding solvent, and the solvent employed in said last-named Washing step being also miscible in water, and diluting and removing the eluate containing the last solvent by washing the impregnated leather in water.

3. A method for restoring the original appearance of leather which has been impregnated throughout the leather with a polymerized wood rosin impregnant to increase wear, for better resistance to water and chemicals, greater flex life and ability to Withstand high temperature and pressure, comprising the steps of washing said impregnated leather in a solvent for the impregnant comprising acetone for a time period-sufficient to dissolve only the impregnant in the surface portions of the impregnated leather, said solvent being miscible with water, and diluting and removing the resulting eluate before said solvent dries by washing the impregnated leather in water.

4. A method for restoring the original appearance of leather which has been impregnated throughout the leather with a rubber impregnant, to increase wear, for better resistance to water and chemicals, greater flex life and ability to withstand high temperature and pressure, comprising the steps of washing said impregnated leather in a hydrocarbon solvent for the impregnant comprising gasoline for a time period sufiicient to dissolve only the impregnant in the surface portions of the impregnated leather, washing said impregnated leather before the hydrocarbon solvent dries in a second solvent which is miscible with both said first solvent and water and in which said impregnant is insoluble, said second solvent comprising acetone, and diluting and removing the eluate containing the second solvent before said second solvent dries by washing the impregnated leather in water.

5. A method for restoring the original appearance of leather which has been impregnated throughout the leather with an impregnant consisting of rubber and polymerized wood rosin, to increase wear, for better resistance to water and chemicals, greater flex life and ability to withstand high temperature and pressure, comprising the steps of washing said impregnated leather in a hydrocarbon solvent for said rubber impregnant comprising gasoline for a time period suificient to dissolve said rubber impregnant only in the surface portions of said impregnated leather, washing the impregnated leather before the first solvent dries in a second solvent which is miscible with both said first solvent and water and in which said impregnant is insoluble for a time period sufficient to dissolve said rosin impregnant only in the surface portions of'said impregnated leather, said second solvent comprising acetone, and diluting and removing the eluate containing said second solvent by washing the impregnated leather in water before said second solvent dries.

OTHER REFERENCES The Spotting Manual of the Drycleaning lndustry,,revised (2nd) edition, June 1946, pages 93, 123, 196, 203, 204 and 220. 

1. A METHOD FOR RESTORING THE ORIGINAL APPEARANCE OF LEATHER WHICH HAS BEEN IMPREGNATED THROUGHOUT THE LEATHER WITH AN IMPREGNANT SELECTED FROM THE GROUP CONSISTING OF RUBBER, OIL, WAX, AND POLYMERIZED WOOD ROSIN, TO INCREASE WEAR, FOR BETTER RESISTANCE TO WATER AND CHEMICALS, GREATER FLEX LIFE AND ABILITY TO WITHSTAND HIGH TEMPERATURE AND PRESSURE, COMPRISING THE STEPS OF WASHING SAID IMPREGNATED LEATHER IN A SOLVENT FOR THE SELECTED IMPREGNANT SAID SOLVENT BEING SELECTED FROM THE GROUP CONSISTING OF GASOLINE, VARSOL, GLYCOL ETHER, ALCOHOL AND KETONES, FOR A TIME PERIOD SUFFICIENT TO DISSOLVE ONLY THE IMPREGNANT IN THE SURFACE PORTIONS OF SAID IMPREGNATED LEATHER, REMOVING THE RESULTING ELUATE BY WASHING SAID IMPREGNATED LEATHER BEFORE SAID SOLVENT DRIES WITH A SECOND ORGANIC SOLVENT WHICH IS INERT TO SAID LEATHER AND WHICH IS MISCIBLE WITH SAID SELECTED SOLVENT AND WITH WATER, AND IN WHICH SAID IMPREGNANT IS INSOLUBLE, AND DILUTING AND REMOVING THE ELUATE CONTAINING THE SECOND ORGANIC SOLVENT BY WASHING THE IMPREGNATED LEATHER IN WATER. 